1. Field of the Invention
The invention relates to a system for fastening a rail which has a rail foot, a web positioned thereon and a rail head. The system according to the invention comprises in this case a carrying plate and a tensioning clamp held on the carrying plate. This tensioning clamp has a central portion for bracing the tensioning clamp on the carrying plate, at least one torsion portion branching off from the central portion in the lateral direction and a holding arm which is connected to the torsion portion via a curved transition portion, extends, starting from the transition portion, counter to the torsion portion and exerts via the free end of its end portion a resilient holding-down force on the rail foot of the rail to be fastened. In this case, the length of the torsion portion and the course of the transition portion are adapted to each other in such a way that at least the transition portion is guided without supports laterally past a region of the carrying plate that is associated with the central portion of the tensioning clamp.
2. Background of Related Art
A fastening system of this type is offered by the Applicant under the name “System KS with SKL 24”, “SKL 24” denoting the specific type of tensioning clamp used in the known system.
In the known system, configured on the carrying plate are two ribs which extend over the length of said carrying plate measured in the longitudinal direction of the rail to be mounted and delimit between them a portion in which, when the system is fully assembled, the foot of the rail which is then fastened is positioned. The ribs serve on the one hand as lateral stops which delimit transverse movements of the rail that occur when a rail vehicle passes over it. On the other hand, the ribs are used in the known system for fastening the tensioning clamp via which the holding force required for holding down the rail is applied resiliently to the rail foot.
In accordance with the basic principle known from DE 20 2004 020 752 U1, the ω-shaped “SKL 24” tensioning clamp used in the known system is configured in such a way that its torsion portions and holding arms have a maximum spring deflexion and, in conjunction therewith, maximum resilience. For this purpose, the known tensioning clamp has a looped central portion, from the ends of which a respective torsion portion, which is substantially straight in its configuration, issues in the direction of the respective side. The torsion portions then each merge with a transition portion which is curved back, viewed from above, through 180° in the direction of the central portion and is in turn adjoined by a respective holding arm which is straight in its configuration and runs substantially parallel to the torsion portion associated with the respective side. The clear width between the torsion portions and the holding arm respectively associated with them is in this case, viewed from above, substantially constant and corresponds in this case to the thickness, measured transversely to the longitudinal extension of the rail to be fastened, of the rib plus an excess which is required to receive the rib, in the thickness direction thereof, with play into the space surrounded by the torsion portions and holding arms.
In the known system, the holding arms of the tensioning clamps exert, as in all fastening systems equipped with tensioning clamps of this type, in the fully assembled state the required holding forces on the rail via the free end of the end portions of said holding arms.
The tensioning clamp is braced on the carrying plate in the known system via a nut screwed onto a tensioning bolt. The tensioning bolt is positioned at one end in a recess formed centrally in the upper side of the respective rib and is guided at its other end through the opening bounded by the central portion.
In practical use, the “System KS with SKL 24” described hereinbefore has fulfilled the expectations placed on this system. However, it occurred that the holding arms were positioned with their free ends on the rail foot with such imprecision that, under the loading, which occurs in practice, of the rail and fastening system, there was a risk of sliding-off from the rail foot.
In addition, the assembly of the known system has proven problematic. Thus, it can occur, in particular in the case of automatic assembly under the rough conditions prevailing on site, that the tensioning clamp rotated under the action of the assembly and tensioning forces and automatically left the position on the rib required for optimum functioning thereof.